1. Field of the Invention
The present invention generally relates to a method for dry cleaning processing chambers, and more particularly to a method for dry cleaning metal etching chambers.
2. Description of the Prior Art
Semiconductor processing involves a number of different chemical and physical processes whereby minute integrated circuits are created on the substrate. As the geometric size of semiconductor devices become ever so smaller, the ability to maintain the uniformity and accuracy of critical dimensions becomes strained. Many of the processes carried out within semiconductor processing reactors leave contaminant deposits on the wall of the process chamber which accumulate and become the source of particulate matter that""s harmful to the creation of a semiconductor device. Contaminant deposit buildup on semiconductor processing chamber walls can be particularly significant when metal etching processes are carried out in the chamber. An important way to improve quality and overall efficiency in fabricating devices is to clean the chamber effectively and economically.
In general, the manufacturing of integrated circuit devices includes the use of a plasma etching chamber, which are capable of etching selected layers defined by a photoresist mask. The processing chambers are configured to receive processing gases while a radio frequency (RF) power is applied to one or more electrodes of the processing chamber. The pressure inside the processing chamber is also controlled for the particular process. Upon applying the desired RF power to the electrodes, the process gases in the chamber are activated such that a plasma is created. The plasma is thus configured to perform the desired etching of the selected layers of the semiconductor wafer.
During an etching process of a semiconductor wafer in a plasma reactor, polymer can be built up on the chamber walls, gas distribution plate (GDP) and interior parts. Over time, failure to clean the residue from the chamber walls often results in degraded, unreliable processes and defective substrates. Without frequent cleaning procedures, impurities from the residue built up in the chamber walls can migrate onto the substrate. Particularly, when the polymer peeling occurs, the yield kill rate can be higher than 10%. Providing an efficient, non-damaging clean chamber is often able to enhance performance and quality of the devices produced. Two methods of cleaning a processing chamber are in-situ cleaning (also known as dry cleaning) and wet cleaning.
In an in-situ cleaning operation, process gases are evacuated from the processing chamber and one or more cleaning process gases are introduced. Energy is then applied to promote a reaction between the gases and any residues that may have accumulated on the process chamber""s interior surfaces. Residues on the process chamber""s interior surfaces react with the cleaning process gases, forming gaseous by-products which are exhausted from the processing chamber, along with unreacted portions of the cleaning process gases. The cleaning process is followed by the resumption of normal processing. In contrast to an in-situ cleaning procedure, in which the processing chamber remains sealed, a wet cleaning procedure is performed by breaking the processing chamber""s vacuum seal and manually wiping down the chamber""s interior surfaces. Such a wet cleaning operation affects a processing system""s throughput in a worse way than a dry cleaning operation does. When a wet clean is performed, opening the processing chamber and physically wiping the chamber""s interior surfaces results in more down-time (about 14 to 16 hours), compared to the dry clean which only takes minutes, because the process must subsequently be re-stabilized.
When polymer is built up on the processing chamber""s interior surfaces, the particle out of control rate is extremely higher resulting in decreased yield. Moreover, when a sudden power interruption occurs, the vacuum pump fails, or the software crashes, the polymer built up on the processing chamber""s interior surfaces will start peeling off, thus a very time-consuming wet clean operation is needed. A wet clean procedure is normally performed to remove residues that are not entirely removed by the in-situ cleaning process, and thus slowly accumulate over time. After longer periods of time, typically about 9000 RF-minutes (150 RF-hour), a wet clean is required. The delay due to the down time required for cleaning also represents a substantial loss in production yield. Clearly, it is desirable to minimize the amount of cleaning time required in order to improve the throughput of wafers through the processing chamber. That is to say, to extend the mean time between clean (MTBC) is critical to achieve the goal. The method used here pertains to a wet clean. Therefore, improved methods for cleaning semiconductor processing chambers is needed. In particular, the cleaning methods should be capable of removing polymer built up on the processing chamber""s interior surfaces to achieve a high yield and maintaining throughput of the substrates in the plasma reactor.
The present invention is directed towards a method for cleaning the processing chamber of a substrate processing system used in processing operations such as the deposition and/or etching of substrates. In accordance with the present invention, a method is provided for dry cleaning a metal etching chamber. This method comprises the step of introducing a first cleaning process gas into the processing chamber at a first flow rate. A plasma is formed from the first cleaning process gas and maintained for a first time period. Next, repeating the step of introducing the cleaning process gas, a second cleaning process gas is introduced into the processing chamber at a second flow rate and maintained the plasma for a second time period. As a result, the present invention is capable of removing polymer built up on the processing chamber""s interior surfaces to achieve a high yield and maintaining throughput of the substrates in the plasma processing system.
It is another object of this invention that a cleaning process gas is provided for dry cleaning a processing chamber.
It is a further object of this invention that a two-step cleaning method is provided for dry cleaning a processing chamber.
It is another further object of this invention that a method for extending the mean time between cleaning is provided.
It is another further object of this invention that a method for reducing the particle out of control rate is provided.
In one embodiment, a method is provided for dry cleaning a processing chamber. This method comprises the step of introducing a first cleaning process gas into the processing chamber at a first flow rate. A plasma is formed from the first cleaning process gas and maintained for a first time period. Next, repeating the step of introducing the cleaning process gas, a second cleaning process gas is introduced into the processing chamber at a second flow rate and maintained the plasma for a second time period. The method further comprises the step of generating a plasma by applying RF energy to the first and second cleaning process gases, wherein the RF energy is about 800 W applied to the first electrode. The method further comprises the step of applying a power of about 4 W to the second electrode, wherein the second electrode is also a substrate holder. Thus, the polymer built up on the holder can also be removed. The method further comprises the step of evacuating the first cleaning process gas from the processing chamber between the first and the second time periods while maintaining the plasma. As a result, the present invention is capable of removing polymer built up on the processing chamber""s interior surfaces to achieve a high yield and maintaining throughput of the substrates in the plasma processing system.